There's a standard: 'IATA regulations'.
Here's the info on Virgin's requirements
Guidelines for Pet Containers
The following container guidelines are designed to protect the welfare of dogs and cats travelling with us, whilst also complying with occupational health and safety legislation. We reserve the right to refuse carriage of pets which are not travelling in a container which complies with the following requirements:
The container must be:
Supplied by yourself or purchased from Toll Air Express (within Australia).
In good repair so that the dog or cat cannot escape from it.
Not too small for the dog or cat.
Lined with absorbent material so that no water or excreta can escape.
Strong enough to withstand damage.
Made of metal or a polypropylene material and must not have any wheels attached.
(if two part rigid plastic containers) - the top and bottom or side parts must be secured by screws or nut and bolt.
Must have escape proof hinges and latches & be adequately locked.
When weighed complete with dog or cat, not exceed 65kgs for Australian Domestic or New Zealand Domestic flights.
Not exceed 120cm long x 70cm wide x 80cm high. Must not be collapsible.
There are heaps of companies that organise the flight of your pet, drop them off at the airport etc.
I don't know how many go from Aus to overseas though.
You can also do it yourself.